Embodiments of the present invention relate to the deposition of silicon dioxide layers in the fabrication of electronic circuits.
Electronic circuits, such as integrated circuits, display circuits, memory circuits, and power circuits, are being made ever smaller to increase portability and computing power. Silicon dioxide layers are used in a variety of applications in the fabrication of the active and passive features of the electronic circuits. In one application, silicon dioxide layers are used in the fabrication of multilayer etch-resistant stacks, as for example disclosed in U.S. Pat. No. 6,136,511, entitled “Method of patterning substrates using multilayer resist processing”, to Reinberg et al., and filed on Jan. 20, 1999, which is incorporated by reference herein in its entirety. An exemplary multilayer stack comprises a base resist layer, a middle spacer layer of silicon dioxide that serves to protect the underlying base resist, and a top imaging resist layer that is sensitive to energy, such as light, X-ray or electron energy. A high resolution pattern can be created in the thin imaging resist layer using lithographic processes. Thereafter, this pattern is transferred to the underlying spacer and resist layer to create a multilayer stack. However, it is difficult to form a spacer layer of silicon dioxide over the photoresist layer without damaging or eroding the underlying photoresist layer. This is because conventional silicon dioxide layers are often deposited at temperatures in excess of 200° C. At these temperatures, the underlying photoresist layer is eroded by the active oxygen ions in the plasma used to deposit the silicon dioxide on the photoresist. Reducing the silicon dioxide deposition temperatures can reduce photoresist damage, however, low temperature deposition processes often result in the deposition of a non-conformal silicon dioxide layers. Further, active radicals in the plasma, such as O−2, OH−, or Cl−2, can modify the photosensitive structure of the photoresist layer to provide poor patterning results. Thus, it is difficult to deposit spacer coatings of silicon dioxide on a resist layer at low temperatures or without damaging or eroding the resist layer.
In another application, silicon dioxide layers are used in the fabrication of through-silicon vias (TSV) which are used to connect electrically the active and passive features in different, vertically stacked, silicon plates. In TSV fabrication methods, through holes are etched in a silicon plate, and filled with an electrical conductor to serve as a vertical interconnect access structure. In such structures, a silicon dioxide layer can be used to line the walls of the through holes before deposition of the metal-containing material therein. The silicon dioxide liner can, for example, serve as an insulating layer, diffusion barriers, hermetic seal, moisture resistance, or still other reasons. However, in the process for fabricating TSV features, a plurality of silicon plates are bonded to one another with an adhesive which flows and can even degrade at temperatures above 200° C. Conventional silicon dioxide processes operate at higher temperatures and cannot be used for the fabrication of TSVs.
For various reasons that include these and other deficiencies, and despite the development of various methods of depositing silicon dioxide layers, further improvements in the deposition of silicon dioxide are continuously being sought.